Organic light emitting elements used as light sources in organic display panels, organic display devices, organic light emitting devices, etc., are light emitting elements that make use of electroluminescence in organic material. In a case of a top emission type organic light emitting element, for example, a thin layer (bottom electrode) composed of aluminium, silver, or similar, is formed on a substrate composed of glass. Further, on the thin layer are layers including a hole-injection layer composed of an oxide of a transition metal, an organic light emitting layer composed of a polymer material, an electron-injection layer composed of barium, and a top electrode composed of aluminium.
The hole-injection layer of such an organic light emitting element is, for example, formed by reactive sputtering using oxygen plasma and a target material composed of a transition metal. Specifically, first, as shown in FIG. 23A, a substrate 904 on which a bottom electrode 903 is formed is set up on a substrate holder 902 that is positioned inside a vacuum container 901, and a target material 906 is set up on a target material holder 905 that is positioned inside the same vacuum container 901. Next, as shown in FIG. 23B, argon gas and oxygen gas is supplied to the vacuum container 901 and sputtering is performed. As a result, as shown in FIG. 23C, a surface of the target material 906 is oxidized, forming a surface layer 906a composed of an oxide of the transition metal, and, as shown in FIG. 23D, the oxide of the surface layer 906a of the target material 906 is transferred to the bottom electrode 903, forming a hole-injection layer 907.
However, oxygen plasma used in reactive sputtering has the characteristic of very easily oxidizing aluminium, silver, etc. Thus, in an organic light emitting element that has the hole-injection layer 907 formed by reactive sputtering, an oxidized film 908 formed by oxidation of aluminium, silver, or similar, is often formed on a surface of the bottom electrode 903. This is a cause of a decrease in light emission efficiency of such an organic light emitting element. For example, when an oxidized film 908 composed of silver oxide is formed, the light emission efficiency of the organic light emitting element is decreased due to the oxidized film 908 impeding light reflection of the bottom electrode 903, which is a reflective electrode. Further, when an oxidized film 908 composed of aluminium oxide is formed, since the oxidized film 908 has a characteristic of high electrical resistance, the drive voltage of the organic light emitting element increases, causing the light emission efficiency of the organic light emitting element to decrease.
Thus, as an organic light emitting element in which formation of the oxidized film 908 on a surface of the bottom electrode 903 is unlikely, an organic light emitting element has been proposed in which a light-transmissive electrically-conductive layer composed of indium tin oxide (ITO) or similar is formed on the bottom electrode 903 (Patent Literature 1).